MONTPELIER — A state rebate program to encourage residents to go solar has helped to install 775 small-scale solar electricity systems since 2006, but the state’s largest residential solar company fears a reduction in funding could curtail that growth by making the investment costlier for homeowners.

SunCommon, which has installed 248 residential solar systems in Vermont in the last year, and Gov. Peter Shumlin urged the Legislature on Monday to continue to fund the program.

“This is not time to pull back on an extraordinary success,” Shumlin said at an event celebrating SunCommon’s anniversary.

The company, which employs 53 people, hopes to install 500 more systems on homes and businesses this year. Its model is to make solar power accessible by installing small-scale systems with no upfront costs to the homeowners.

A homeowner pays a monthly fee, essentially shifting his or her payment for electricity from a utility to a financing agency that pays for the solar panels. SunCommon has a number of financial arrangements, including lease and loan options.

The lease option suited Joanne Heidkamp and her family in South Burlington, after they had taken steps to save energy through energy efficient programs and installing compact fluorescent light bulbs.

“It seemed like the next logical step would be to use our big west-facing roof to actually generate energy and yet the upfront costs seemed really daunting to us,” she said.

Over the winter, the system made about half the energy the family used. By March, it was making as much as the family used, and in April it has exceeded what is needed.

“So it’s very easy to see over a course of a year that we will be putting more energy onto the grid than we are taking off,” Heidkamp said.

But SunCommon officials worry that a program that gives an average household a rebate of about $2,000 to $4,000 for a system that could cost between $12,000 and $25,000 after federal and state incentives could be cut.

The Vermont House is considering about $1.9 million and a Senate committee $1.2 million for the clean energy development fund, which funds the small scale renewable energy incentive program.

“At this pace that’s expected to run out in early summer,” SunCommon co-president Duane Peterson said.

House lawmakers have dismissed Shumlin’s plan to pay for energy programs through a new tax on charitable betting tickets called break-open tickets.